Power transmission system



Oct.8,1935'. B FRANK 2,016,632 POWER TRANSMISSION SYSTEM Filed June 28, 1952 4 Sheets-Sheet l Oct. 8, 1935, FRANK POWER TRANSMISSION SYSTEM 4 Sheets-Sheet 2 Filed June 28, '1932 -vc-7' B my 077W I I I I I I I I I I I I I I u u I I I I I 1 I I I I I I n I Oct. 8, 1935. FRANK I POWER TRANSMISSION SYSTEM Filed June 28, 1932 4 Sheets-Sheet 5 Oct. 8, 1935. B. FRANK POWER TRANSMISSION SYSTEM Filed June 28, 1952 4 Sheets-Sheet 4 B1 i iem Patented Oct. 8, 1935 rowan TRANSMISSION SYSTEM Benjamin Frank, Bandocnl, Java, Dutch East Indies Application June28, 1932, Serial No. 619,749. In the Netherlands March 1, 1932 '1 Claims. (01. 192-35) This invention relates to unimproved coupling mechanism.

The main object of the invention is a mechanism whereby a driving and a driven element a can be coupled to and uncoupled from each other smoothly and without shocks.

An essential feature of the coupling in accordance with the invention is, that the driving and the driven element are each constrained to rotate positively with individual screw threads adapted during coupling to engage each other, one of the said elements being provided with a totally closed cylinder filled with -a suitable liquid and cooperatingwith an axially movable 16' piston, which is fitted with the male orHthe female screw thread with which one of said elements isiconstrained to rotate, and adapted, on the angular speed of the one thread exceeding that of the other, to. move axially in the cylinder and, during the coupling operation, thereby brought about, to gradually close the free passage for the liquid from one side oi the piston to the other. The cylinder wall, is preferably provided internally with axial grooves, the depth of which gradually decreases towardstheend of the cylinder. Q

During the coupling operation, the liquid trapped by the piston acts as a hydraulic shock absorber, so that said operation takes place very 0 smoothly and without shocks.

Although the invention is primarily intended for motor vehicles, it is by no means limited thereto, as it can be applied with equal advan-, tage .to the propeller shaft of vessels, to trans-,

mission gear, for instance, for machine-tools,

etc.

- The invention will now be described in furthcr detail with reference to the annexed drawings, which illustrate some embodiments there- 4 of andin whichz Fig. 1 is a longitudinal sectional view of a semi-automatic change-speed gear for a motor uehicle, including a coupling with hydraulic shock absorber, and electromagnetic operating mechanism,

Fig. 2 is a cross sectionalview along the'line IIII in Fig. 1,

Fig. 3 is a longitudinal sectional view of a somewhat modified coupling, including a mea coupling of modified construction, certain parts being shown in section for the sake of clearness.

The coupling shownin Figs. 1 and 2 comprises.

a, cylinder 9 closed by a cover 2, which is bolted thereto so as to ensure a perfectly. tight joint, 5

and formed as a flywheel of the motor of. the vehicle, to which the coupling is applied. The cover 2 is keyed or otherwiseflxedly secured to the driving shaft 8 and provided on its inner face with a boss I, which projects into an axial l0 recess in the end face of a hollow shaft "and forms a journal for said shaft.

The cylinder 9 is provided with a filling aperture tightly closed by a screw plug L; The deduced left hand side neck portion of the cy l6 der 9 forms a bearing for the left hand side end of the hollow shaft IS, the end face of which is fitted with bevelled dogs or teeth 2|; The tightness of the joint between the cylinder 9 and the hollow shaft I6 is ensured bya gasket 20 l9. a i

The neck of the cylinder O-is provided externally with a. gear rim 21 and internally with a female screw thread, which has a pitch of and engages with the male thread 28 on a socket 2 9. 25

On its outer cylindrical face, the hollow shaft l6 has longitudinal splines engaging with corresponding grooves or slots in an annular member adapted forsliding movement over said shaft and composed of an externally threaded sleeve ll 80 integral with a piston 4. Consequently, sleeve II and piston 4 are constrained to rotate positively with shaft It. The piston 4 has a plurality of passages 5 adapted to be sealed by a common valve disk 3.

Screwed within the reduced central portion of cylinder 9 is a bush l4 having axial grooves in its inner face and mounted on corresponding splines formed on a nut member I5, which has freedom of axial movement within narrow limits. It will 60 thus be understood that the nutmember I5 is constrained to rotate positively with the bush I4 and with the cylinder 9.-

A coil spring l8 tends to urge the flanks of the thread of nut l5 into contact with those of sleeve 45 l l, a collar I3 on the right hand side end of bush H limiting the axial movement of the nut II to the right.

The nut member I5 and thewall of cylinder 9 are provided with a plurality of axial passages l 5 and 9', respectively, providing for a free communication between the cylinder spaces on either side of said nut. a V

The internal diameter of the cylinder 9 between a and b exceeds the external diameter of piston 4. The next cylinder portion between b and c, with which the piston 4 has a sliding fit, is provided on its inner wall with a plurality of grooves I8, the depth of which gradually decreases towards the left, so that at c the bottoms of said grooves are substantially flush with the inner cylinder wall.

The wall of the bore of the hollow shaft I8 is axially grooved, said grooves engaging with mating splines formed on a coupling shaft l1 adapted for sliding movement under the thrust of a coiled spring l2 housed within said bore and bearing against the bottom thereof. That portion of the coupling shaft ll, which projects from the bore of hollow shaft l6, has a collar 28 and dogs or teeth 24, adapted for coaction with similar dogs on the right hand side end face of the driven shaft, designated by as.

The driven shaft 88 is supported by suitable bearings of the stationary casing or housing 28 and furnished with axial splines engaging corresponding grooves in the inner wall of a sleeve 84. Thus, said sleeve 84, the right hand side end face of which is fitted with .teeth 82, is adapted for axial sliding motion over shaft 88 by the thrust of a coiled spring 35.

The collar 28 of coupling shaft l1 bears against a shoulder on the right hand side end face of the socket 29, which face is provided with dogs 22 adapted for cooperation with the teeth 2| of the hollow shaft I 8. On the left hand side of thescrew thread 28, the socket 28 has a somewhat reduced outer. diameter, the next portion to the.

left, which has an increased diameter, being fitted externally with a gear rim II. and internally with dog clutch teeth 88 adapted to engage the teeth 82 of sleeve 84.. On its-left hand side, the socket 28 has a collar 58 and spaced therefrom a nut 58, between which parts a freely rotatable ring 81 is mounted so as to be locked against axial displacement relative to the socket.

The diameter of gear rim 21' exceeds that of gear rim 8|. Both rims act as sun wheels of a planetary gear, which comprises planet wheels rotatably mounted within a casing 28.

Each planet wheel comprises a relatively small spur gear 58 meshing with the sun wheel 21, and a relatively large spur gear 55 cooperating with the sun wheel 8| of the socket 28, which is arranged for axial sliding movement so as to remain in mesh with the spur gear 55.

Mounted around casing 28 is an annular armature l2 splined thereon but having freedom of a small axial displacement relative thereto. Said armature coacts with an annular magnet 1| adapted to be energized on depression of a spring loaded switch button l8l.

The ring 51 serves for throwing in and throwing out the spur wheels of the variable-speed gear mechanism. For this purpose, it is provided at its top with two lugs 51' through which a cross rod 88 is passed, and at its bottom with .trunnions 8|. These trunnions are engaged by a fork 82 provided with trunnions 83 by means of which it is pivotally mounted in bearings of the stationary casing or housing 28. At its top, said fork 82 has two lugs 82' engaged by a cross rod 58 in parallel relation with rod 88.

The left hand end of the intermediate shaft 88 is hollow and is fitted externally with a gear rim 81. The variable speed gear mechanism proper comprises a plurality of spur wheels 88, 88, 82, 84, which are freely revoluble on the driven shaft 86, the right end of which is supported in the hollow end of the shaft 88. Gears 81, 88, 88 and mesh with the gear 88. 5

On the driven shaft 88 are mounted for axial sliding movement three grooved clutch rings 88, 8|, 88 constrained to rotate positively with said shaft and adapted to be actuated by rods I9, 8 I, 84, respectively, which are slidable in the casing 28. 10

ecured to said rods are actuating forks 88 (for the 4th and the 3rd speed), 88 (for the 2nd and the 1st speed), and 85 (for the reverse), respectively. Furthermore, said rods are each provided with one or two pawls, each loaded by a spring 16 18 tending to urge it into inoperative position. Mounted in the wall'of casing 28 are three spring loaded pins 82 adapted to cooperate with notches in the rods 18, 8|, 84, so as to retain these in their operative positions in a manner well known.

It is to be understood that each of the rods 18 and 8| has two pawls I8 18 18 and 18', one for the 4th and 2nd speed, respectively, and one for the 3rd and 1st speed, respectively. Rod 84, however, is furnished with one pawl 18' only.

Each of said pawls 18'18 has two projections 15, 18' I5 I8 I5 18 and 15 18, respectively,

for engagment with the cross rod 58, or with the cross rod 88 as the case may be said rods being adapted to move towards or away from one another when the socket 28 with the ring 51 is axially displaced.

The pawls 18'18* are adapted to be depressed by the thrust of the soft iron cores 18 of coils 14, when the latter are energized.

The modus operandi of the coupling mechanism will now be described.

For uncoupling the driven element from the driving element the operator depresses button l8! so as to close the contact l-8la, whereby magnet 40 II is energized and armature l2 attracted, so that the casing 28 is braked and arrested.

With the casing 28 locked against rotation, the planet wheels 53, 55 are constrained to rotate about their axes. Gears 21, 8|, which, till now, rotated at'equal angular speeds, are thus caused to revolve at different speeds, the speed of gear 8| exceeding that of gear 21.

Owing thereto, screw 28 will assume a'greater angular speed than has the nut formed by the neck of cylinder 9, since the latter continues to rotate at a substantially constant speed. As a consequence, screw 28 is moved axially relative to its nut, i. e. socket 29 moves towards the hollow shaft I8. In doing so, the socket urges the coupling shaft H to the right, so thatsaid shaft is moved further into the hollow shaft l8, thereby compressing spring I2.

It is pertinent here to remark that, as long as the coupling is thrown in, piston 4 assumes 50 its extreme position to the left, so that its screw ll fully engages nut l5 and the system I1, l8, ll,

4 is constrained to rotate positively with cylinder 8. As soon as the socket 28 moves to the right, the dog clutch teeth 24 disengage the teeth 25, so that the driven shaft 88 is released from the coupling shaft l1. The-socket 28 will then continue its axial movement, until the teeth 22 engage the teeth 2|, whereby to shaft I6 and, consequently, also to sleeve H with piston 4 the same angular speed is imparted as has'the socket 28. Ultimately, screw 28 fully disengages the nut provided in the neck of cylinder 8.

As long as casing 28 is arrested, gear II and socket 28 will rotate in the same direction as, but 7 filled, will flow through the grooves NJ in the cylinder wall and also past valve disk 3 through the passages in piston 4. This outward movement of piston 4 will continue until sleeve II' has fully disengaged nut member l5 and piston 4 abuts against nut 6, when piston 4 is permitted to rotate freely.

When the shaft 36 is to be coupled to the driving shaft 8, then the circuit of magnet 1| is again interrupted, whereby armature 12 is released and again with the casing 26 permitted to rotate.

Since the casing 26 is now again released, the planet wheels 53, 55 will no longer rotate about their own axes, so that the angular speed of sun wheel 3| no longer exceeds that of sun wheel'21. Coupling shaft 11 tends to push socket 29 to the left, under the thrust of spring i2, so that the thread of screw 28 again engages the nut in the neck of cylinder 9.

The socket 29 will, under these circumstances,

rotate slower than cylinder 9, until screw 26 again fully engages its nut and socket 29 has returned into its initial position. Only then socket 29 will again revolve with the same angular speed ascylinder 9.

Meanwhile coupling shaft I1, which, with hollow shaft i6 and piston 4 in its extreme right hand position, is rotating at the same angular speed as cylinder 9, moves under the thrust of spring l2 to the left until it clutches the intermediate shaft 36. Owing to the load acting thereon, the driven shaft at that moment is. stationary; anyhow its angular speed is smaller than that of shaft l1. If, now, the teeth 24 and 25 engage one another, the coupling shaft 11 with associate parts l6 and 4 will be braked by the driven shaft. Cylinder 9, however, continues its rotation and the nut member l5, which is permanently urged into contactwith the thread of sleeve ll under the thrust of spring [6, will be screwed upon the stationary or slowly revolving sleeve I l so that piston 4 is moved to the left.

On its way to the left, the piston 4 will displace the liquid, which now can escape only through the grooves II) in the inner cylinder wall, since valve 3 has closed the passages 5 under the action of the liquid pressure As the piston moves on, the liquid offers an increasing resistance, because the depth of said grooves decreases. The shock produced by the throwing in of the coupling is transmitted by the piston 4 to the liquid, and as the resistance of the liquid gradually increases, this shock will be gradually absorbed.

The increasing resistance encountered by the piston 4 on its way to the left causes sleeve II to be rotated. by the revolving nut member l5, in

the same direction as cylinder 9. So, on its way from b to c the'piston will simultaneously perform a retarded axial and an accelerated rotary.

out the setting of the change-speed gear being affected, since the pawls are then not depressed.

Consequently, the cross rods 59 and 96, which during the coupling operation move towards one another, cannot engage any of the projections of 5 the pawls 16 -18 The coupling and uncoupling during gear changing is brought about by means of a handle I03 on the steering wheel.

For gear changing, the axial movement performed by the socket 29 during the coupling and the uncoupling of shafts 8 and 36 is utilized. When during uncoupling the socket 29 moves towards the right, owing to the excess of rotary speed of the sun wheel 3|, ring 51 will also be moved to the right by the collar 56, whereby cross rod 60 is also forced tothe right and rod 59 is moved to the left by the action of the fork 62.

I By the actuation of the aforesaid handle on the steering wheel, one of the magnets 14 (Fig. l) 20 is energized. Owing thereto, the corresponding core 13 is urged downward, whereby the selected pawl e. g. pawl 18 is depressed and the corresponding projection 15 moved into the path of the rods 59, 6B, which are moving towards each other. Thus, said rods return rod 6| into neutral position, through the projection 15' and the pawl 18', whereby the corresponding ring 9|, which up till that moment clutched one of the gears 99, 92, is also moved back into neutral position.

It now by interrupting the circuit of magnet 1| the casing 26 is released during the coupling of shafts 8 and 36, whereby socket 29 and shaft 11 are;again moved to the left under the thrust of 36 spring I 2, the ring 51 will also be urged to the left by the nut 56, whereby the rods 59 and 60 will move away from one another. Assuming now one of the gear selecting pawls 18-18' to be depressed,'one of its projections will be engaged by 40 one of the rods 59, 66,'which are pushed away from one another by the spring l2. Thereby,- the corresponding rod 19, 6| or. 84 will be moved to the right or to the left and the corresponding ring 86, 9| or 93 will clutch one of the gears 61, 69, 96, 92, 94, whereby the change of gear ratio is completed.

'The contacts of the operating means areso arranged that during uncoupling the circuit for one of the coils 14 isclosed prior to the magnet 1| being energized-and that during coupling (putting in of a speed) the circuit of the magnet 1| is interrupted prior to that of the coil 14. Consequently, one of the pawls 16'16 is necessarily depressed, when during coupling or uncoupling the rods 59, 66 move towards or away from one another.

The coupling shown in Figs. 3 and 4 is of simpler construction than the one in accordance with Figs. 1 and 2. Moreover, it is provided with 0 mechanical, instead of electromagnetic operating gear.

In said construction, the piston 4 is slidabie over the inner faces of splines confining grooves H0 and 2"! in the inner wall of the hydraulic g cylinder 9. Said piston cooperates as a nut with the externally threaded hollow shaft l6, asdistinguished from the device shown in Figs. 1 and 2. in which the piston 4 is axially slidable over the hollow shaft I6 and integral with a screw 70 cooperating with a nut 15 in cylinder 9.

Grooves 2l6 have a greater depth than grooves J H6 and also serve to guide splines 204 of the pistonl. As shown in Fig. 5 the grooves 2H] and H0 are wound along a helix having a pitch exceeding and opposite that of the thread on the hollow shaft '5. In said modification, the piston will have a tendency to be screwed to the left.

If, therefore, the piston has moved to the right owing to an excess of angular speed of screw l6, the flanks of the threads on the piston will always be urged against those of screw l6, so that no special spring (I in Fig. l) is required. During the sliding movement of the piston, therefore, the piston 4, the cylinder 9 and the shaft I6 rotate at different speeds.

Mounted intermediate between the two parts, of which the casing 26 is composed, is a freely rotatable ring 30 provided internally with teeth meshing with those of the spur gear 55, and externally with a screw thread wound in a direction opposite that of screw I6. Moreover, casing 26 has a plurality of dog clutch teeth 44 arranged for cooperation with a stop tooth 43 adapted, against the thrust of a spring 40, for limited sliding motion in the direction of rotation of casing 26, over a shaft 48 secured in a block 45. Said block is provided with a cam face 45a, loaded by springs 39, and slidably mounted on two rods 38 secured to the cover 31 of the stationary casing 20.

In the position shown in Fig. 3, block 45 is locked by a latch 46, springs 39 are tensioned, and tooth 43 disengages teeth 44.

Also slidably mounted on rods 38 is a half nut 52, the thread of which is adapted to mesh with that of ring 30. A spring 5|, however, tends to retain the half nut 52 out of engagement with the screw thread of said ring. The left hand side end face of nut 52 is chamfered so as to form a cam face.

Journaled in bearings of the cover 31 is a shaft 4| carrying a lever or pedal 4| provided with a spring latch 42 adapted to cooperate with a projection of cover 31. Shaft 4| further carries two levers 49, intermediate between which are supported two freely rotatable rollers 48, 50. In the illustrated, i. e. neutral position, roller 46 engages the horizontal top face of block 45, whereas the half nut 52 is urged against roller 59 by the spring 5|. A latch 41, arranged for lifting latch 46, is kept in engagement with both levers 49 under the action of its spring 41', whereas a shoulder of latch 46 is pressed in downward direction, by a spring 46', on the top face of cover 31.

Latch 41 has a lateral projection 65 for engaging a horizontal cross rod 64 mounted between two lever arms 66.

The rod 8| is provided with three pawls 11', 111i, 11 viz, for the lst speed, for neutral and for the 2nd speed, respectively, whereas rod 19 is also fitted with three pawls, viz, for the 4th speed. for neutral and for the 3rd speed, respectively. Rod 84, however, is furnished with only two pawls, for neutral and for the reverse, respectively.

By rotation of a cam shaft 61, cams 61a, 61b, 610, etc. mounted thereon act upon the corresponding pawls so as to depress them. If a neutral pawl is depressed, the levers 66 are lifted by a special cam arranged on the cam shaft 61 diametrically opposite each of the neutral cams.

The levers 66 are rotatable about a shaft 68 and adapted to lift the latch 41 owing to the cooperation of its lateral projection 65 with cross rod 64.

Rotation of the cam shaft 61 is brought about by a lever 69 cooperating with a toothed segment 10 in mesh with a pinion on the cam shaft 61,

the ratio between the diameters of the pitch circles of said pinion and said segment being such as to cause a full revolution of cam shaft 61 when lever 69 is turned through about 90.

Lever 69 is adapted to be operated by a handle on the steering wheel of the motor vehicle.

Fig. 1 of the drawings represents the position of the parts when the vehicle is at rest and the driven shaft 36 has been uncoupled from the driving shaft 8. As shown the piston 4 assumes its extreme right hand position and the screw H is completely disengaged from the nut l5. The screw 28 is in full engagement with the nut formed by the neck of cylinder 9.

The modus operandi of the embodiment according to Figs. 3 and 4 will now be described.

For uncoupling the driven element from the driving element, lever 4| (Fig. 3) is depressed so as to be locked by the spring latch 42. Thereby, the levers 49 lift the latch 41 and, consequently, also latch 46, so that block 45 is released and permitted to move to the left under the thrust of springs 39. Tooth 43 is now adapted to engage one of the teeth 44 of casing 26, which rotates at the angular speed of cylinder 9, that is to say, of the driving shaft 8. Initially, tooth 43 is moved, against the thrust of its spring, over shaft 40 in the direction of rotation of casing 26, whereby the shock is absorbed. Thereupon, casing 26 is braked by tooth 43 and arrested.

As described above with regard to the embodiment according to Figs. 1 and 2 screw 28 will now assume a greater angular speed than has the cylinder 9, so that piston 4 moves to the right, and this outward movement continues until the piston has fully disengaged the screw thread on shaft 5, whereby the uncoupling action is completed.

When the driven shaft 86 is to be coupled to the driving shaft 8, lever 4| is unlatched. As

will be understood, the block 45 at that moment" so that the flanks of nut 52 are forced against those of ring 30. During this angular motion of levers 49, roller 48 drops into contact with the horizontal top face of block 45 at the right hand side of cam 45a.

As long as the casing 26 is arrested, the planet wheels -53 rotate in a direction opposite that of cylinder 9. Consequently, ring 30 will also be rotated in a direction opposite that of cylinder 9 by the spur gears 55, which mesh with the internal gear rim of said ring. The thread of ring 30 will now engage with the half nut 52 and move the latter to the right, i. e. towards the block 45. Since the half nut 52 and the block 45 are both mounted on the rods 38, ring 30 will urge both the half nut 52 and the block 45 to the right, against the thrust of springs 39, until tooth 43 disengages toot-h 44. Latch 46 will then, by the action of its spring 48, drop into the space on the left hand side of block 45 so as to lock the latter. During the movement of block 45 to the right under the action of ring 30, roller 48 will ride uphill over cam face 45a and thereby lift levers 49.

Since the casing 26 is now again released, spur gears 53 and 55 will no longer turn about their be screwed off ring 30, and moved to the left,

until it has fully disengaged said ring. Moreover, the half nut 52 is urged to the left by spring 6|, so that it remains out of contact with ring As described above with regard to the embodiment according to Figs! 1 and 2 coupling shaft I1 is now forced to the left under the thrust of spring l2 until it clutches theintermediate shaft 36, whereby shaft II will be braked, so that the piston 4 will be screwed upon the stationary or slowly revolving shaft l6. The coupling .action is then completed. I T The coupling and uncoupling during gear changing is brought about by meensof the lever 69. By the actuation of said" lever cam shaft 61 is turned and is cams pointing down, 111: is depressed tion 15 moved into the path of the rods 59, 60.

If a neutral, cam on shaft 61 depresses the pawl I'ln another diametrically opposed cam on said shaft 61 will simultaneously lift the levers 66, whereby cross the latch 41 and whereby the selected pawl I the uncoupling mechanism is put into operation,

' manner that they then engage the teeth whereby the said socket owing to the locking of casing 26. will now move towards each other and return rod el into neutral position, through the projection 15 and the pawl 'lln, whereby thecorresponding clutch ring is also moved back into' neutral position.

If now by further rotation of cam shaft 61 levers 66again drop downward, levers49 are depressed the action of spring the casing 26 will be released, so that socket 29 and shaft H are again moved to the left under the thrust of spring l2. The ring 61 will also be urged to the left by the nut 56, whereby the rods 59 and 60 will move away from one another. Meanwhile one 6lb, 61c, 61d has depressed the corresponding gear selecting pawl, which with its projectionwill be engaged by one of the rods 59, 60, which are one another by the spring l2.

Thereby, the moved to the right or'to the left'and the corresponding clutch ring will clutch one of the gears ratio is completed.

From the above ent that my novel coupling a freewheel. If, namely, the tates faster than the driving shaft 8, for instance, on accidental gain of speed of the vehicle, piston 4 will unscrew from nut IS. The teeth 32 of the sleeve34ar'e beveled in such a 33 of thrust of spring 35, also begins to rotate faster than cylinder 9, the consequence being that the screw 28 is unscrewed from its nut, coupling shaft I1 is urged to the right, and the dogs 22 of screw 28 ultimately engage the hollow shaft IS with associate'parts, i. e. piston 4 with screw 1 I. Thus, as long as shaft 36 rotates faster than cylinder 9, freewheeling will occur. When the fuel valve of the motor is closed, cylinder 9 may even remain stationary, while shaft 36 continues its rotation.

In motor vehicles, the use of the described power transmis ion system has, amongst others,

description it will be apparis adapted to act as driven shaft 36 rothe socket 29, under the of fuel and lubricant, especially closure of the fuel valve the driven shaft.

.shown in Figs.

of magnet special switch. set with one of its neutral and the corresponding proiec-.- braking cylinder, via the sun wheels gaged by sleeve braking power between wheels. and 21.

t with the female thread'ofthe-cylirider,

41 whereby corresponding rod 19, 6| will bewitha driven adapted to rotate positively with a hollow shaft,

relative to one within said hollow shaft and adapted for axial very economical consumption in busy traffic. being that during slowing is avoided, as on driven shaft is imthe motor, so that the the advantage of mediately released from crank shaftneed'not under all conditions follow'the driven shaft.

The provision of the sleeve 34 makes it possible to establish a connection between the driven shaft 86 and the driving cylinder 9, so that the braking power of the motor can be utilized, after closure of the fuel valve, for retarding the To this end,in the arrangement 3 and 4, lever 41 should be depressed and, if necessary, latched, whereas with the construction illustrated in Figs. 1 and. 2

should be depressed, or the circuit ll should be closed by means of a By these means, the casing 26 is braked and arrested so as to establish a connection between the rotating shaft 36 and the 21, 3i and the planet wheels 55-53, since socket 26 is en- 34. Under these conditions, the of. the motor is transmitted to shaft 36 in a ratio responsive to the speedratio button I I) l WhatI claim is:-- I 1. In means for coupling -adriving element with a driven element; a totally closed cylinder secured to the driving element and provided internally with a female thread, an annular piston working in said cylinder, a male thread provided side of the piston and cooperating thread provided on the inner side of the piston and having a pitch smaller than and opposite that of the femalethread of the cylinder, a male thread adapted to rotate positively with the driven element and to cooperate with thefemale thread of the piston, ajpassage adapted to ensure communication between the space on either side of the piston, and a mass of liquid completely filling up the cylinder, the cross sectional area being adapted to be gradually reduced on axial movement of the piston during the coupling operation when the female thread of the piston engages the male thread on the driven element. i 7

2. In means for coupling .a driving element element, a male screw thread a female screw'thread adapted for cooperation withsaid male thread and to rotate positively with the driving element, a totally closed cylinder one of said screw threads and axially movable in said cylinder 1 v another, a coupling slidingmovement therein but prevented from rotation relative thereto, resilient means interposed between saidhollow shaft and said couplingv shaft, means for coupling said coupling shalt element, a passage adapted to ensure communication between the spaces on either side of the piston, and a mass of liquid completely filling up said cylinder, the cross sectional area of said passage being adapted to be gradually reduced on axial movement of the piston during the coupling operation.

3. In means for coupling a driving element with a driven element, a male screw thread with said driven a female adapted to rotate positively with a hollow shaft, a female screw thread adapted for cooperation with said male thread and to rotate positively with the driving element, a totally closed cylinder secured to the driving element and revoluble relative to said hollow shaft, a piston carrying one of the said screw threads and axially movable in said cylinder on rotation of said screw threads relative to one another, a second female screw thread provided on the cylinder, a coupling shaft located within said hollow shaft and adapted for axial sliding movement therein but prevented from rotation relative thereto, resilient means interposed intermediate between said hollow shaft and said coupling shaft, means for coupling. said coupling shaft with said driven element, a socket mounted for rotation on the driven element and adapted on axial movement to uncouple the driven shaft from the coupling shaft, a male screw provided on said socket and cooperating with the said second female thread of the cylinder, means for coupling said socket with said hollow shaft, a passage adapted to ensure communication between the spaces on either side of the piston, and a mass of liquid completely filling up said cylinder, the cross sectional area of said passage being adapted to be gradually is reduced on axial movement of the piston duringthe coupling operation,

4. In means for coupling a driving element with a driven element, a male screw thread adapted to rotate positively with a hollow shaft, 9. female screw thread adapted for cooperation with said male thread and to rotate positively with the driving element, a totally closed cylinder secured to the driving element and revoluble relative to said hollow shaft, a piston carrying one of the said screw th eads and axially movable in said cylinder on rotation of said screw threads relative to one another, a second female screw thread provided on the cylinder, a couplingshaft located within said hollow shaft and adapted for axial sliding movement therein but prevented from rotation relative thereto, resilient means interposed intermediate between said hollow shaft and said coupling shaft, means for coupling said coupling shaft with said driven element, a socket mounted for rotation on the driven element and adapted on axial movement to uncouple the shaft from the coupling shaft, a male screw provided on said socket and cooperating with the said second female thread of the cylinder, means for coupling said socket with said hollow shaft, a gear rim on said socket, a second gear rim on the cylinder, a casing adapted for rotation about said socket, means for arresting said casing, a pinion mounted for rotation in said casing and having two gear rims of different diameters in mesh with the said gear rims, respectively, a passage adapted to ensure communication between the spaces on either side of the piston, and a mass of liquid completely filling up said cylinder, the cross sectional area of said passage being adapted to be gradually reduced on axial movement of the piston during the coupling operation.

5. In means for coupling a driving element with a driven element, a male screw thread adapted to rotate positively with a hollow shaft, a female screw thread adapted for cooperation with said male thread and to rotate positively with the driving element, a totally closed cylinder secured to the driving element and revoluble relative to said hollow shaft, a piston carrying one of the said screw threads and axially movable in said cylinder on rotation of said screw threads relative to one another, a second female screw thread provided on the cylinder, a coupling shaft located within said hollow shaft and adapted for axial sliding movement therein but prevented from rotation relative thereto, resilient means interposed intermediate between said hollow shaft and said coupling shaft, means for coupling said coupling shaft with said driven element, a socket mounted for rotation on the driven element and adapted on axial movement to uncouple the driven shaft from the coupling shaft, a male screw provided on said socket and cooperating with the said second female thread of the cylinder, means for coupling said socket with said hollow shaft, a gear rim on said socket, a second gear rim on the cylinder, a casing adapted for rotation about said socket, means for arresting said casing, a pinion mounted for rotation in said casing and having two gear rims of different diameters in mesh with the said gear rims, respectively, a spring loaded annulus mounted for axial sliding movement on the driven element but prevented from rotation relative thereto, means for coupling said annulus with said socket on the angular speed of the driven element exceeding that of the driving element, a passage adapted to ensure communication between the spaces on either side of the piston, and a mass of liquid completely filling up said cylinder, the cross sectional area of said passage being adapted to be gradually reduced on axial movement of the piston during the coupling operation.

6. In means for coupling a driving element with a driven element, a male and a female screw thread adapted to engage each other and to rotate positively the one with the driving and the other with the driven elements, a tot-ally closed cylinder secured to one of said elements and filled with liquid, a piston carrying one of said screw threads and axially movable in said cylinder on rotation of said screw threads relative to one another, a pass-age adapted to secure communication between the spaces on either side of the piston, the cross sectional area of said passage being adapted to be gradually reduced on axial movement of the piston, the male and female screw threads being so developed and arranged that the male thread turns out of the female thread when the speed of the driven element exceeds the speed of the driving element.

'7. A coupling means as claimed in claim 6 char acterized by the provision of a freely rotatable casing, braking means associated with said casing, shafts mounted in said casing, a gear on the driving element, pinions on said shafts in mesh with said gear, and a gear on each of said shafts having a greater number of teeth than the pin ion, a toothed rim adapted to be coupled with the driven element and engaged by the last mentioned gears.

BENJAMIN FRANK. 

